ZOOPHYTES. 337 



hy one end, while the other stretches out horizontally, 

 thus surrounding the slender column. Each of these 

 ■sacs is an ovarian capsule, and contains several ova of a 

 brilliant yellow or crimson hue. Thus we have the 

 second form, that of the reproductive polypes. 



In some places single ovarian capsules stand up alone 

 from the fleshy carpet, agreeing in every respect with 

 those which we have just examined, except that they 

 are sessile, instead of being carried by a polype. 



The fourth form is that of the tentacular polype. Here 

 and there, from amidst the forest of shorter polypes, both 

 alimentary and reproductive, white threads are seen pro- 

 truding, which extend to a length four or five times as 

 great as theirs, and hang down or loosely float in the 

 water. They are found on the outskirts of the whole 

 compound structure, and at each extremity of the long 

 diameter of the mouth of the supporting shell ; so that 

 they must, in their natural condition, reach to the ground, 

 along which the crab-tenanted shell is carried, enabling 

 the Zoophyte to seize and appropriate the atoms scattered 

 by the crab whenever he takes his meals. The tips of 

 these organs are covered with a dense pavement of large 

 thread-cells; and they must doubtless perform the office 

 of general purveyors to the composite animal. 



But still more remarkable, more extraordinary than all 

 we have been considering, are the objects which are now 

 in view in the field of the microscope. You see a number 

 of bodies, which Dr. Wright calls ophidian or spiral 

 polypes ; and which, as he truly observes, are " like small 

 white snakes, closely coiled in one, two, or three spirals, 

 and grouped immediately round the mouth of the shell." 

 The habits of these polypes are still stranger than their 

 forms. " When touched they only draw their folds more 

 closely together. But if any part of the polypary, however 

 distant from them, be irritated, the spiral polypes uncoil, 

 extend and lash themselves violently backwards and for- 



